// #define 符号名称 字符序列

#include <iostream>

#define PI      3.14159265
#define MyPay   25.00

int main() {
    float r = 10.0;

    float area_circle = PI * r * r;
    float TotalPay = MyPay * 40.0;

    using std::cout;

    cout << "\npi的值是 " << PI;
    cout << "\nMyPay的值是 " << MyPay;
}

//  g++ -fexec-charset=GBK ch02/2_9.cpp && ./a
